US1086300A - Rectifying apparatus. - Google Patents

Description

0. A. KRAUS.

RBGTIFYING APPARATUS. APPLICATION FILED NOV.21,1910.

Patented Feb. 3, 1914.

'-1nore anodes and a UNITED STAflJES T OFFICE.

CHARLES A. KR AUS, DE -NEWTON HIGHLANDS, MASSACHUSETTS.

RECTIFYI NG APPARATUS.

To a ta /10m it may com c/'11.

Be it known that '1, CHARLES A. Keane, a citizen of the United States and resident oflYcwton Highlands, in the county of Middlesex and State oi Massachusetts, have invented new and useful Improvements in Rectifying Apparatus, of which the following: is a specification.

My iny'ention relates to vapor electricapparatus and has for its object the provision of such circuit and distribution arrange Incnts as will'minimize and practically eliminate the difliculties and dangers due to short circuit arcing in the exhausted containers of such apparatus.

For illustration otmy invention 1 take the mercury arc"rcctitie* as a cha act-cristie example of vapor electric apparatus in the operation of which short circuit arcing has heretofore proved a source of difficulty and of actual danger to the structure and integrity of the ap iaratus. As is well known, a mercury arc rectifier consists essentially of a highly exhausted envelop or container within which are provided two or. mercury cathode, the anodes being C()I1Sll'tl(l0(l usually of solid conducting materials. The anodes being connected respectively to the outer terminals of a suitable exciting rcactance and the midor neutral-point of the reactance being connected through a load circuit to the mercury cathode, the anodes allow the current to flow through the rarefied vapor in the container to the mercury cathode but refuse to allow current to flow in the reverse direction under normal proper working conditions. Ilv this check valve action, only one- -half wave of the impressed alternating current, flows through either anode and the two half waves succeed each other by phase differences of .180" and combine in the load circuit to Form a continuous, pulsatinc unidirectional currcnt ot which the wave :lorm is dependent upon the rcactance in the load circuit.

For reasons which are not yetwell understood, it, often happens that the check alve action 01 an anode tails to manifest itself, so that the current instead of flowing in the proper normal manner flows from one anode to the other. Since there is no can Specification of Letters Patent.

Application filed November 21. 1910.

Patented Feb. 3, 1914. Serial No. 593,297.

sidcrable impedance in the circuit when the current passes between the anodes, the current not only is the proper operation of the ap paratus interrupted but, what is more Serious, the integrity of the apparatus itself is endangered. This phenomenon is known as short circuit arcing. Although attempts have been made heretofore to prevent short circuit arcing by increasing the length of path between the anodes, this has not proved effective since the tendency to are increases both with increase of potential and current, and short circuit arcs inevitably occur in rectifiers of comparatively large energy-capacity. For this reason the utilities of mercury are rectifiers have been greatly restricted.

My invention is characterized bV the in troduction into rectifier circuits of opposed, and, preferably, accu 'ately balanced reactances in such manner that under the normal operating conditionsthese reactances do not affect the current to any practical degree but so that they may act as control reactances to keep the current below a predetermined safe value in case a short circuit are should occur.

In the drawing: hereto annexed there is illustrated in diagram an apparatus which exemplifies this invention inits application to the rectification of a single phase alternatin; current. y Y

Referring to the diagram, A, A. represent; mercury arc rectifiers of the usual construction in which I), E and I) E are the main or working anodes, (l and C the mercury cathodes and If and I the auxiliary or starting anodes. The starting anodes may be put in circuit with a source ofcoutinuous unidirectional controlled by resistance .imlicated at ll and B. This portion of the apparatus'is provided merely for starting it and my iinproveincnt is not concerned with it. The reactances which represent the sources of alternatingcurrent for the two rectitiers A and A are represented by L, R, and L, R. These rcactances are substantially identical, and are so formed and associated with a source of alternating current that the terminal poles L, L and R .s respectively are reaches abnormally high Values so that current as K which may be suitably similar in respect to current-direetion.- The reactanccs L R and L R may thus he. encrgized inductively by coils T and T from altei'nat-ing current mains M M. Between the source reactances and the rectificrs I provide nnitually opposed, balanced, or neutralizing reactances P, Q, and P, Q; rcspectirely. the inc nbcrs of each of these pairs being associated through'a magnetic circuit 0, O, respectively. The cathodes C and Cf of the two rectitiers A and A" are connected in parallel through. lines 1 t, to the line in which the load H is interposed and from the line 5 to the mid points of the souree-rcactances in parallel through lines 5 a, s. The main or working anodes of each rectifier are connected respectively to the outer terminals of one 01' the'source reactspectively through lines Z, 1", to the outer terminals ot' the exciting reactance L, -r, the anodes D and E are connected respectirelv through the lines Z, r, to the outer terminals oi the XCltlllQ'lCfiCl'tUlCQ L, R.

The line Z includes the governing react ance P and the line Z includes the rea'etance Q which is opposed. to or balanced by the reactance 1 Likewise the line '1 includes the rcactance P and the line r the reactance.

Q, so that the lines or connections rein magnetically similar terminals of the two exciting reactances pass through gor'crning r. actances which are prct'e ably perfectly balanced.

Assume now that the entire apparatus is in operation to rectify single phase alternating current converting it into a pulsating unidirectional current through the load ll. During a one-half phase current will D and E being connected rewhilemutually opposed and rcnl lion's from the opposite terminals oi. the exciting reaclaiares through line 7-, a", that is. the magnetic circuit 0. to), are each altcrnatirely working and idle, as the are cnergized in parallel from not. \Vhen, however, the next hall phase is established, the check valve action of anodes 1) and 1) comes into play, lines 1. and Z become inactive and the current flows through 1', r to anodes E and E, cathodes C and C, and thence as before through t, Z through load H, line S and lines s,,s to the mid-points ot the exciting reactanccs.

Under the above described normal working conditions, the governing reactances P, Q or P, Q as the case may be, oiiset and the two sources. or I 3 tential wave during the hall cycle is i preaching its maximum. value.

l l l cuit arcing in the two rectilicrs. Only in the .in so doing ClQVGlOP' the -lull reactive power of the Widing and, since the in fcasc of current in winding P, due. to the short cir O cult supposed is not accou'ipanied by corresponding increase in the wining (-1,, teedingthe winding 1), the diilerence in the current values in P and (Qt must turtherrnor overcome the unbalanced reactive power-of the winding P, acting in series W. "h 3 t limit the current flow. "lhe dangerour heretofore possibly destructive action o short circuit are is therefore suppressed the apparatus preserved from injury. i such a short circuit are in one of the r liers A, A, the establishment of the nes halt cycle will cause the rectifier to resume its normal operation,

The only condition in such an apparatus as herein described under which short cir cuit arcing can cause undesirabl or (lain gerous high currents to iiow through the that of Sli'DillliZtIlQOllS short cir- Cir rectifiers 1s 100 case of the chccl-z valve action oi, say, anodes I) and D ceasing to function siinultancously can the current due to short circuit arcs reach abnormally high "values.

The phenomenon of short circuit arcing occurs in (i-rectifier or analogous apparatus at intervals which depei'idcn the construction of the rectifier, and also on the. current and potential and when it occurs it endures at the 11108, for half a cycle in a. properly designed apparatus. Therefore, to enable slrort circuitarcing to produce alniornially or dangerously high clu'rents in an apparatus arranged according to this invention, the short circuit arcing inust coincide in the two rectiliers within a period of time considcrihl less than that occupied by a halt cycle, since it is sale to a rmic that the short circuit are is produced only when. the poan" vGut in th'-- der to demonstrate the practical lll'lflll! of an apparatus such above desc" from the dangers of short circuit are let us assume that this PllGIlOllltiilUIl occur at any time during an entire wave period; and let i a. suine also the apparatus is i single phase alter I more, in order to he as tar 1,ose,soo

safe side in this calculation, let us assume the rectifiers to be'so constructed that either of the rectifiers will short circuit on the average of once in 15 minutes. Then the probability of a short circuit are taking place in any one-half cycle in either of the rectifier-s isrepresented' by the fraction:

Then if two rectifiers of this kind are working under the conditions named, the probability that the short circuit arcs in the two rcctiliers will coincide in any given half cycle is represented by the fraction:

Otherwise expressed, short circuit arcs may be expected to coincide on the average once in 108 x10 cycles, br one coincidence in JJTQXIO" minutes, or 1120 days of 24 hourseach. In other words, the application of my invention lengthens the mean period of dangerous arcing from once in 15 minutes to something over once in three years. For commercial purposes this practically eliminates arcing as a factor of 0pcration, because at the present time no rec- 'til'icrs on the market have a life which approaches three years. bo far as I am informed the life of present connncrcial rectiliers averages about 1200 working hours.

It should be noted that the introduction of the above described invention does not de rease the elliciency ot' a rectifying sys tem because the capacity of the system is doubled while the governing rcactanres have no seriousinl'hience on the ellicicncy ol' the system, since only their ohmic resistance is normally operative.

' What I claim and desire to secure by Let lcrs latent is:

1. ln apparatus for rectifying alternating currents, two complete rectifying units, two sources of alternating current, two pairs of mutually opposed. rcarlau es, lead: from similar tcrn'iinals of the alternating current sources passing rcsiwmively through mulually opposed. rczu iancc-nicinl'lcrs and thence, one to an anode o'l one rectifying unit, the other to an anode of the other rcctilying unit, and a connection common to the calhodes of the two rectifying units to points neutral with respectto tl alternating current sources.

2. In a vapor electricapparatus, two con; tainers, each having a cathode and anodes, two sources of ahcrnal ing current, two pairs of mutually opposed reactances, leads from similar terminals-of the alternating current sources passing respectively through inututerminals of the source reactances passingrespectively each through one of a pair of mutually opposed rcactance. members, and thence one to an anode of one contain r, the other to an-anode of the other-c0ntainer, and a connection common to the two cathodes, and to the mid-points of the'source reactances. 4

4. The combination with transforming ap paratus comprising two secondary windings,

oftwo current rectifiers connected to said" windings, and two impedance devices each comprising two windings that are respec-.

tively interposed in the connections between the reotifiers and the secondary Windlngs of the transformers, the connections to each rcctilicr including a winding of each impedance device. 5. Thecombination with transforming apparatus comprising!wo secondary windings, of two current rcctilicrs connected to said windings, and two impedance devices each con'iprising two normally com )lcmcntary windings that are res 'iertivcly interposed in the connections between the rcctitiers' and the secondary windingrs' ol the transl'ornicrs, the connections in each rectifier including! a winding of each impedance device.

Signed by me at Boston, \lassaclnisctts, this 3rd day of November, 1910.

CHARLES A. KRAUS.

\Yil ucsses:

(nannies l). iVoonm-ann', ()mN Honours.

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